diff --git a/apis/spaces/v1alpha1/simulation_conditions.go b/apis/spaces/v1alpha1/simulation_conditions.go
new file mode 100644
index 0000000..e5cc3e5
--- /dev/null
+++ b/apis/spaces/v1alpha1/simulation_conditions.go
@@ -0,0 +1,83 @@
+// Copyright 2024 Upbound Inc
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package v1alpha1
+
+import (
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	xpv1 "github.com/crossplane/crossplane-runtime/apis/common/v1"
+)
+
+// Condition types.
+const (
+	// TypeAcceptingChanges indicates the simulated control plane is accepting
+	// changes. All changes detected while this condition is true will appear in
+	// the change summary.
+	TypeAcceptingChanges xpv1.ConditionType = "AcceptingChanges"
+)
+
+// Reasons a simulation is or isn't accepting changes.
+const (
+	ReasonSimulationStarting   xpv1.ConditionReason = "SimulationStarting"
+	ReasonSimulationRunning    xpv1.ConditionReason = "SimulationRunning"
+	ReasonSimulationComplete   xpv1.ConditionReason = "SimulationComplete"
+	ReasonSimulationTerminated xpv1.ConditionReason = "SimulationTerminated"
+)
+
+// SimulationStarting indicates a Simulation is still starting. It isn't yet
+// ready to accept changes.
+func SimulationStarting() xpv1.Condition {
+	return xpv1.Condition{
+		Type:               TypeAcceptingChanges,
+		Status:             corev1.ConditionFalse,
+		LastTransitionTime: metav1.Now(),
+		Reason:             ReasonSimulationStarting,
+	}
+}
+
+// SimulationRunning indicates a Simulation is running, and ready to accept
+// changes.
+func SimulationRunning() xpv1.Condition {
+	return xpv1.Condition{
+		Type:               TypeAcceptingChanges,
+		Status:             corev1.ConditionTrue,
+		LastTransitionTime: metav1.Now(),
+		Reason:             ReasonSimulationRunning,
+	}
+}
+
+// SimulationComplete indicates a Simulation is complete, and no longer ready to
+// accept changes. A SimulationComplete Simuluation's simulated control plane
+// keeps running until the Simulation is terminated.
+func SimulationComplete() xpv1.Condition {
+	return xpv1.Condition{
+		Type:               TypeAcceptingChanges,
+		Status:             corev1.ConditionFalse,
+		LastTransitionTime: metav1.Now(),
+		Reason:             ReasonSimulationComplete,
+	}
+}
+
+// SimulationTerminated indicates a Simulation is terminated. The simulated
+// control plane is deleted when a simulation is terminated.
+func SimulationTerminated() xpv1.Condition {
+	return xpv1.Condition{
+		Type:               TypeAcceptingChanges,
+		Status:             corev1.ConditionFalse,
+		LastTransitionTime: metav1.Now(),
+		Reason:             ReasonSimulationTerminated,
+	}
+}
diff --git a/apis/spaces/v1alpha1/simulation_types.go b/apis/spaces/v1alpha1/simulation_types.go
new file mode 100644
index 0000000..71bf3c4
--- /dev/null
+++ b/apis/spaces/v1alpha1/simulation_types.go
@@ -0,0 +1,211 @@
+// Copyright 2024 Upbound Inc
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package v1alpha1
+
+import (
+	"reflect"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+
+	xpv1 "github.com/crossplane/crossplane-runtime/apis/common/v1"
+)
+
+// +kubebuilder:object:root=true
+// +kubebuilder:storageversion
+// +kubebuilder:subresource:status
+// +kubebuilder:printcolumn:name="SOURCE",type="string",JSONPath=".spec.controlPlaneName"
+// +kubebuilder:printcolumn:name="SIMULATED",type="string",JSONPath=".status.simulatedControlPlaneName"
+// +kubebuilder:printcolumn:name="ACCEPTING-CHANGES",type="string",JSONPath=".status.conditions[?(@.type=='AcceptingChanges')].status"
+// +kubebuilder:printcolumn:name="STATE",type="string",JSONPath=".status.conditions[?(@.type=='AcceptingChanges')].reason"
+// +kubebuilder:printcolumn:name="AGE",type="date",JSONPath=".metadata.creationTimestamp"
+// +kubebuilder:resource:scope=Namespaced,categories=spaces
+
+// A Simulation creates a simulation of a source ControlPlane. You can apply a
+// change set to the simulated control plane. When the Simulation is complete it
+// will detect the changes and report the difference compared to the source
+// control plane.
+type Simulation struct {
+	metav1.TypeMeta   `json:",inline"`
+	metav1.ObjectMeta `json:"metadata,omitempty"`
+
+	Spec   SimulationSpec   `json:"spec"`
+	Status SimulationStatus `json:"status,omitempty"`
+}
+
+// +kubebuilder:object:root=true
+
+// SimulationList contains a list of Simulations.
+type SimulationList struct {
+	metav1.TypeMeta `json:",inline"`
+	metav1.ListMeta `json:"metadata,omitempty"`
+	Items           []Simulation `json:"items"`
+}
+
+// SimulationSpec specifies how to run the simulation.
+type SimulationSpec struct {
+	// ControlPlaneName is the name of the ControlPlane to simulate a change to.
+	// This control plane is known as the Simulation's 'source' control plane.
+	// +kubebuilder:validation:MinLength=1
+	// +kubebuilder:validation:XValidation:rule="self == oldSelf",message="The source controlplane can't be changed"
+	ControlPlaneName string `json:"controlPlaneName"`
+
+	// DesiredState of the simulation.
+	// +kubebuilder:default=AcceptingChanges
+	// +kubebuilder:validation:Enum=AcceptingChanges;Complete;Terminated
+	// +kubebuilder:validation:XValidation:rule="oldSelf != 'Complete' || self == 'Complete' || self == 'Terminated'",message="A complete Simulation can only be terminated"
+	// +kubebuilder:validation:XValidation:rule="oldSelf != 'Terminated' || self == oldSelf",message="A Simulation can't be un-terminated"
+	DesiredState SimulationState `json:"desiredState"`
+
+	// CompletionCriteria specify how Spaces should determine when the
+	// simulation is complete. If any of the criteria are met, Spaces will set
+	// the Simulation's desired state to complete. Omit the criteria if you want
+	// to manually mark the Simulation complete.
+	// +optional
+	CompletionCriteria []CompletionCriterion `json:"completionCriteria,omitempty"`
+}
+
+// SimulationState represents the lifecyle state of a simulation.
+type SimulationState string
+
+const (
+	// SimulationStateUnknown indicates the simulation's state is unknown.
+	SimulationStateUnknown SimulationState = "Unknown"
+
+	// SimulationStateStarting indicates the simulation is starting. It's not
+	// yet ready to accept changes.
+	SimulationStateStarting SimulationState = "Starting"
+
+	// SimulationStateAcceptingChanges indicates the simulation is accepting
+	// changes.
+	SimulationStateAcceptingChanges SimulationState = "AcceptingChanges"
+
+	// SimulationStateComplete indicates the simulation is complete. Changes
+	// made once a simulation is complete won't appear in the change summary.
+	// It's still possible to connect to and explore a complete simulation.
+	SimulationStateComplete SimulationState = "Complete"
+
+	// SimulationStateTerminated indicates the simulation has terminated. You
+	// can explore the change summary, but the simulation is no longer
+	// accessible.
+	SimulationStateTerminated SimulationState = "Terminated"
+)
+
+// A CompletionCriterion specifies when a simulation is complete.
+type CompletionCriterion struct {
+	// Type of criterion.
+	// +kubebuilder:validation:Enum=Duration
+	Type CompletionCriterionType `json:"type"`
+
+	// TODO(negz): Make Duration an optional field once we support other types
+	// of completion criteria.
+
+	// Duration after which the simulation is complete.
+	Duration metav1.Duration `json:"duration"`
+}
+
+// A CompletionCriterionType is a type of criterion.
+type CompletionCriterionType string
+
+const (
+	// CompletionCriterionTypeDuration specifies that a simulation is complete
+	// after a specified duration. The duration is relative to when the
+	// simulation entered the AcceptingChanges state.
+	CompletionCriterionTypeDuration CompletionCriterionType = "Duration"
+)
+
+// SimulationStatus represents the observed state of a Simulation.
+type SimulationStatus struct {
+	xpv1.ResourceStatus `json:",inline"`
+
+	// SimulatedControlPlaneName is the name of the control plane used to run
+	// the simulation.
+	// +kubebuilder:validation:MinLength=1
+	// +optional
+	SimulatedControlPlaneName *string `json:"simulatedControlPlaneName,omitempty"`
+
+	// ControlPlaneData exported from the source control plane and imported to
+	// the simulated control plane.
+	// +optional
+	ControlPlaneData *ControlPlaneData `json:"controlPlaneData,omitempty"`
+
+	// Changes detected by the simulation. Only changes that happen while the
+	// simulation is in the AcceptingChanges state are included.
+	// +optional
+	Changes []SimulationChange `json:"changes,omitempty"`
+}
+
+// ControlPlaneData exported from the source control plane and imported to the
+// simulated control plane.
+type ControlPlaneData struct {
+	// ExportTimestamp is the time at which the source control plane's resources
+	// were exported. Resources are exported to temporary storage before they're
+	// imported to the simulated control plane.
+	ExportTimestamp *metav1.Time `json:"exportTimestamp,omitempty"`
+
+	// ImportTiemstamp is the time at which the source control plane's resources
+	// were imported to the simulated control plane.
+	ImportTimestamp *metav1.Time `json:"importTimestamp,omitempty"`
+}
+
+// A SimulationChange represents an object that changed while the simulation was
+// in the AcceptingChanges state.
+type SimulationChange struct {
+	// Change type.
+	// +kubebuilder:validation:Enum=Unknown;Create;Update;Delete
+	Change SimulationChangeType `json:"change"`
+
+	// ObjectReference to the changed object.
+	ObjectReference ChangedObjectReference `json:"objectRef"`
+}
+
+// A SimulationChangeType represents the type of a change.
+type SimulationChangeType string
+
+// Simulation change types.
+const (
+	SimulationChangeTypeUnknown SimulationChangeType = "Unknown"
+	SimulationChangeTypeCreate  SimulationChangeType = "Create"
+	SimulationChangeTypeUpdate  SimulationChangeType = "Update"
+	SimulationChangeTypeDelete  SimulationChangeType = "Delete"
+)
+
+// A ChangedObjectReference represents a changed object.
+type ChangedObjectReference struct {
+	// APIVersion of the changed resource.
+	APIVersion string `json:"apiVersion"`
+
+	// Kind of the changed resource.
+	Kind string `json:"kind"`
+
+	// Name of the changed resource.
+	Name string `json:"name"`
+
+	// Namespace of the changed resource.
+	// +optional
+	Namespace *string `json:"namespace,omitempty"`
+}
+
+// Simulation type metadata.
+var (
+	SimulationKind             = reflect.TypeOf(Simulation{}).Name()
+	SimulationGroupKind        = schema.GroupKind{Group: Group, Kind: SimulationKind}.String()
+	SimulationKindAPIVersion   = SimulationKind + "." + SchemeGroupVersion.String()
+	SimulationGroupVersionKind = SchemeGroupVersion.WithKind(SimulationKind)
+)
+
+func init() {
+	SchemeBuilder.Register(&Simulation{}, &SimulationList{})
+}
diff --git a/apis/spaces/v1alpha1/zz_generated.deepcopy.go b/apis/spaces/v1alpha1/zz_generated.deepcopy.go
index 29d856a..c3ec0cb 100644
--- a/apis/spaces/v1alpha1/zz_generated.deepcopy.go
+++ b/apis/spaces/v1alpha1/zz_generated.deepcopy.go
@@ -288,6 +288,65 @@ func (in *BackupStatus) DeepCopy() *BackupStatus {
 	return out
 }
 
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *ChangedObjectReference) DeepCopyInto(out *ChangedObjectReference) {
+	*out = *in
+	if in.Namespace != nil {
+		in, out := &in.Namespace, &out.Namespace
+		*out = new(string)
+		**out = **in
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new ChangedObjectReference.
+func (in *ChangedObjectReference) DeepCopy() *ChangedObjectReference {
+	if in == nil {
+		return nil
+	}
+	out := new(ChangedObjectReference)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *CompletionCriterion) DeepCopyInto(out *CompletionCriterion) {
+	*out = *in
+	out.Duration = in.Duration
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new CompletionCriterion.
+func (in *CompletionCriterion) DeepCopy() *CompletionCriterion {
+	if in == nil {
+		return nil
+	}
+	out := new(CompletionCriterion)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *ControlPlaneData) DeepCopyInto(out *ControlPlaneData) {
+	*out = *in
+	if in.ExportTimestamp != nil {
+		in, out := &in.ExportTimestamp, &out.ExportTimestamp
+		*out = (*in).DeepCopy()
+	}
+	if in.ImportTimestamp != nil {
+		in, out := &in.ImportTimestamp, &out.ImportTimestamp
+		*out = (*in).DeepCopy()
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new ControlPlaneData.
+func (in *ControlPlaneData) DeepCopy() *ControlPlaneData {
+	if in == nil {
+		return nil
+	}
+	out := new(ControlPlaneData)
+	in.DeepCopyInto(out)
+	return out
+}
+
 // DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
 func (in *InControlPlaneOverride) DeepCopyInto(out *InControlPlaneOverride) {
 	*out = *in
@@ -1169,3 +1228,131 @@ func (in *SharedSecretStoreStatus) DeepCopy() *SharedSecretStoreStatus {
 	in.DeepCopyInto(out)
 	return out
 }
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *Simulation) DeepCopyInto(out *Simulation) {
+	*out = *in
+	out.TypeMeta = in.TypeMeta
+	in.ObjectMeta.DeepCopyInto(&out.ObjectMeta)
+	in.Spec.DeepCopyInto(&out.Spec)
+	in.Status.DeepCopyInto(&out.Status)
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new Simulation.
+func (in *Simulation) DeepCopy() *Simulation {
+	if in == nil {
+		return nil
+	}
+	out := new(Simulation)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
+func (in *Simulation) DeepCopyObject() runtime.Object {
+	if c := in.DeepCopy(); c != nil {
+		return c
+	}
+	return nil
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *SimulationChange) DeepCopyInto(out *SimulationChange) {
+	*out = *in
+	in.ObjectReference.DeepCopyInto(&out.ObjectReference)
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new SimulationChange.
+func (in *SimulationChange) DeepCopy() *SimulationChange {
+	if in == nil {
+		return nil
+	}
+	out := new(SimulationChange)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *SimulationList) DeepCopyInto(out *SimulationList) {
+	*out = *in
+	out.TypeMeta = in.TypeMeta
+	in.ListMeta.DeepCopyInto(&out.ListMeta)
+	if in.Items != nil {
+		in, out := &in.Items, &out.Items
+		*out = make([]Simulation, len(*in))
+		for i := range *in {
+			(*in)[i].DeepCopyInto(&(*out)[i])
+		}
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new SimulationList.
+func (in *SimulationList) DeepCopy() *SimulationList {
+	if in == nil {
+		return nil
+	}
+	out := new(SimulationList)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyObject is an autogenerated deepcopy function, copying the receiver, creating a new runtime.Object.
+func (in *SimulationList) DeepCopyObject() runtime.Object {
+	if c := in.DeepCopy(); c != nil {
+		return c
+	}
+	return nil
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *SimulationSpec) DeepCopyInto(out *SimulationSpec) {
+	*out = *in
+	if in.CompletionCriteria != nil {
+		in, out := &in.CompletionCriteria, &out.CompletionCriteria
+		*out = make([]CompletionCriterion, len(*in))
+		copy(*out, *in)
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new SimulationSpec.
+func (in *SimulationSpec) DeepCopy() *SimulationSpec {
+	if in == nil {
+		return nil
+	}
+	out := new(SimulationSpec)
+	in.DeepCopyInto(out)
+	return out
+}
+
+// DeepCopyInto is an autogenerated deepcopy function, copying the receiver, writing into out. in must be non-nil.
+func (in *SimulationStatus) DeepCopyInto(out *SimulationStatus) {
+	*out = *in
+	in.ResourceStatus.DeepCopyInto(&out.ResourceStatus)
+	if in.SimulatedControlPlaneName != nil {
+		in, out := &in.SimulatedControlPlaneName, &out.SimulatedControlPlaneName
+		*out = new(string)
+		**out = **in
+	}
+	if in.ControlPlaneData != nil {
+		in, out := &in.ControlPlaneData, &out.ControlPlaneData
+		*out = new(ControlPlaneData)
+		(*in).DeepCopyInto(*out)
+	}
+	if in.Changes != nil {
+		in, out := &in.Changes, &out.Changes
+		*out = make([]SimulationChange, len(*in))
+		for i := range *in {
+			(*in)[i].DeepCopyInto(&(*out)[i])
+		}
+	}
+}
+
+// DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new SimulationStatus.
+func (in *SimulationStatus) DeepCopy() *SimulationStatus {
+	if in == nil {
+		return nil
+	}
+	out := new(SimulationStatus)
+	in.DeepCopyInto(out)
+	return out
+}